1. Field of the Invention
The present invention relates to a machine learning device and a machine learning method for optimizing timing at which a tool is to be compensated in a machine tool, and a machine tool including the machine learning device.
2. Description of the Related Art
Recently, high accuracy processing in a machine tool has been more and more demanded, and accordingly, a so-called tool compensation that compensates a blade tip position of a tool in consideration of an abrasion amount of a blade tip of the tool of the machine tool and an effect of a thermal displacement of the machine tool is performed.
In a conventional machine tool, the frequency of performing the tool compensation is often determined based on experiences by the operator. Specifically, an extraction inspection of the size of a workpiece processed by the machine tool is performed, and whether or not the operator performs the tool compensation based on a result of the inspection is determined.
In addition, to reduce labor of the operator, a technique of automatically performing a tool compensation has been proposed. For example, JP H07-104813 A describes a numerical controller including a compensation data storage element for storing compensation data as history data each time a tool compensation is performed, and a tool compensation instruction element for automatically instructing a tool compensation with respect to tool data of a processing program instructed by a numerical control machine tool.
Further, JP 2005-202844 A describes a numerical controller including an initial compensation amount input element for inputting an initial compensation amount for compensating a displacement amount of a tool, a compensation amount storage processing element for storing the compensation amount as history data each time a compensation of a tool displacement amount is performed, a tool compensation amount determination element for determining a compensation amount based on the compensation amount input to the initial compensation amount input element and the history data, and a compensation means for compensating a displacement amount of the tool based on the determined compensation amount.
Conventional tool compensations have been performed mainly for maintaining a processing accuracy. In other words, if the frequency of a tool compensation is too low, a processing accuracy of a workpiece lowers and in some cases defective products are produced. However, on the contrary, if the frequency of a tool compensation is too high, there occurs a problem in that a working ratio of a machine tool lowers. An optimal value for the frequency of a tool compensation exists, whereas, in view of two points in terms of processing accuracy and working ratio, an effective method or an element for determining an optimal value of the frequency of a tool compensation has thus never been conventionally proposed.